1. Field of the Invention
The invention relates to a resilient foot insert arranged within a foot molding of a jointless artificial foot for an artificial leg. According to embodiments of the present invention, a first spring has an approximately C-shaped longitudinal section with an opening facing rearward. A second spring, that is connected to the bottom portion of the C-spring, is a leaf spring that extends forward beyond the C-spring and approximately parallel to the sole region. At a front end, the leaf spring projects as far as the toe region.
2. Description of Related Art
It is known to provide a rigid artificial foot configuration, for example, one made of wood, with or without a joint in order to imitate the function of the ankle. It is also known to provide a resilient foot insert made up of leaf springs and sheathed with foam (see, for example, U.S. Pat. No. 4,959,073).
German Patent 40 38 063 discloses a jointless prosthetic foot with a one-piece insert that permits plantar and dorsal flection, as well as axial compression, in the longitudinal section of the foot. This patent discloses an approximately S-shaped design having a top portion including a front segment sloping at an obtuse angle, and a generally rigid angle element connecting the front segment to a central, leaf-spring-like portion that is connected at its opposite end to a bottom portion via an approximately semicircular element. In this case, the rigid angle element extends forward, generally into the metatarsophalangeal joint region.
French Patent 26 40 499 discloses a jointless artificial foot in which the central portion of a sideways approximately U-shaped insert is located approximately in the front third of the length of the sole, while a top leg portion of the U-shaped insert forms a connection to the artificial leg. The U-shaped insert assumes a spring function, which is supplemented by a resilient cushion positioned between the legs of the U-shaped insert, for achieving a certain degree of flexibility when the artificial foot is placed on the ground. However, it has been found in practice that this artificial foot does not allow a natural walking motion.
German Utility Model G 93 15 665.0 also discloses a jointless artificial foot including a foamed-plastic foot molding with a metallic reinforcing body having a U-shaped profile whose leg portions can be moved elastically toward one another under loading. The material thickness decreases approaching the free ends of the legs, while the free ends per se are provided with thickened sections. The free end of the bottom leg is screwed to a leaf spring, while the top leg is connected to a leg-connection part. The leaf spring may be made of carbon fiber or titanium. The interspace between the free U-segments may be filled with a flexible polyurethane foam. The intention for this resilient spring element is to allow foot movement in the manner of a pro-oblique supination about the longitudinal axis of the foot, as well as a natural movement sequence.